PHOTOCHEMICALLY INDUCED FLUORESCENCE DETERMINATION OF BIOMEDICALLY IMPORTANT PHENOTHIAZINES IN AQUEOUS-MEDIA AT DIFFERENT PH VALUES

A simple room-temperature photochemically induced fluorescence (RTPF) method was developed for the determination of several biomedically imp ortant phenothiazines including azure A, methylene blue, thionine, pro methazine and unsubstituted phenothiazine in aqueous solutions. These compounds are weakly or non-fluorescent under these conditions but the ir fluorescence can be induced on UV irradiation. The influence of pH and irradiation time on their excitation and emission fluorescence wav elengths and on their fluorescence intensity was investigated. It was found that the optimum PH values ranged from 2.0 for unsubstituted phe nothiazine to 7.0 for promethazine and 10-13 for the other compounds, the selected irradiation times being between 5 s and 17 min, depending on the compound. Linear calibration graphs were obtained over about t wo orders of magnitude, with relative standard deviations in the range 3.9-6.9%. RTPF limits of detection were between 12 and 70 ng ml(-1) a ccording to the compound. RTPF was applied to the determination of phe nothiazines in urine samples. The mean recoveries ranged from 87 to 11 6%.